Fix Python 3 bugs discovered by pylint
In Python 3 exception instances no longer have a message attribute.
For most exceptions, str(e) or string formatting give the same result.
Fix some renamed modules, module members and functions.
https://fedorahosted.org/freeipa/ticket/4985
Signed-off-by: Christian Heimes <cheimes@redhat.com>
Reviewed-By: Martin Basti <mbasti@redhat.com>